DESIGN

We used data from the French E3N longitudinal prospective cohort.

SUBJECTS

In the total population of 63 726 women who were analyzed, 1887 breast cancer cases were diagnosed during follow-up.

RESULTS

Among postmenopausal women, the risk of ER+/PR+ breast cancer increased with increasing weight, BMI, and both HCs and WCs, although these two associations disappeared after adjustment for BMI. No association was seen with ER-/PR- breast cancers. Among premenopausal women, among the different factors studied, HC only (no association was observed for any of the different factors studied except for HC) was associated with an increased risk of ER+/PR+ breast cancer after adjustment for BMI (hazard ratio (HR)=1.65; (1.04-2.62) when comparing the highest to lowest tertile; P-trend across tertiles=0.03) and of ER-/PR- breast cancer both before and after adjustment for BMI (HR=2.85 (1.33-6.13); P-trend <0.01, and HR=3.13 (1.19-8.27) P-trend =0.02, respectively). In the latter group, the association with HC was observed whatever the WC (HR=2.81 (1.18-6.70) and HR=2.79 (1.16-6.76) in women with high HC/low WC and high HC/high WC, respectively).

CONCLUSION

The increase in risk of premenopausal breast cancer associated with large HC for both ER+/PR+ and ER-/PR- subtypes may provide insight into a specific risk factor for premenopausal breast cancer.